The present disclosure relates to fluids, additives, and methods for use in subterranean operations, and more specifically, to improved methods and additives for scavenging carbon dioxide and/or hydrogen sulfide for use in subterranean formations and fluids.
Carbon dioxide (CO2) is a corroding agent commonly encountered in the production of oil and gas. While dry CO2 is noncorrosive within the range of temperatures encountered during oil and gas production, CO2 in an aqueous phase forms carbonic acid, which corrodes tubings, casings, and other types of well bore and pipeline equipment. Carbonic acid corrosion can erode and ultimately destroy oil and gas conduits, and can also choke production by causing scaling on the inner surface of production conduits or within the producing formation itself. Carbonic acid corrosion can also corrode cement sheathing, compromising the structural integrity and zonal isolation of wellbores. Carbonic acid corrosion is generally greater under conditions of high temperature and low pH, and is also influenced by flow rates within the conduit and the presence of other corrosive agents in the aqueous phase.
Oil and gas reservoirs are often characterized according to whether or not they contain hydrogen sulfide (H2S), a pungent and toxic gas that is also acidic and highly corrosive in the aqueous phase. Aqueous H2S forms highly corrosive sulfides which accelerate conduit and infrastructure erosion and scaling. H2S-containing reserves are described as “sour,” while reserves generally free of H2S are referred to as “sweet.” Corrosion due to carbon dioxide occurs in the production of sweet gas, but is significantly exacerbated in the production of sour gas. Carbon steel tubing, such as coiled tubing for wellbores, is particularly susceptible to corrosion due to aqueous carbonates and sulfides.
Corrosion due to CO2 and sulfide ultimately results in cracking or obstruction of production equipment, such as tubing and other conduits. Prevention of equipment failure due to corrosion requires costly production shutdowns and frequent workovers, and limits the productive life of reservoirs by making continued production economically unfeasible. Thus, it is typically desirable to reduce or eliminate CO2 and, where present, H2S from subterranean formations and well bores to reduce corrosion rates and extend the productive life of hydrocarbon reservoirs.
Although scavengers are often used to convert H2S to a more inert form, the use of CO2 scavengers is not common in the production of oil and gas. H2S scavengers include certain aldehydes, certain amine-based chemicals, triazines, copper compounds, hydrogen peroxide, zinc compounds, and iron compounds. However, the reaction products of many of these compounds are poorly soluble in treatment fluids and/or fluids in the well bore, or may decompose, thereby releasing CO2 or H2S. Moreover, conventional corrosive gas scavengers may have undesirable environmental and/or toxicity profiles, and as such may be impractical to use or prohibited altogether in certain circumstances and/or jurisdictions. Where CO2 scavenging is desired in oil and gas production, separate CO2 and H2S scavengers are typically used, increasing costs and compounding environmental concerns.
While embodiments of this disclosure have been depicted and described and are defined by reference to example embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.